The present invention is directed to a method of manufacturing an otoplastic or an ear adaptor member by providing an elastic-shaped part that can be placed on a carrier member or mandrel. It is likewise directed to an otoplastic for a hearing aid and to an ear adaptor member for a hearing aid which is worn behind the ear and has the ear adaptor extending into the ear canal. The carrier part, for example, can be a housing of an in-the-ear hearing aid, for example which is custom made or the shell of a module of an in-the-ear hearing aid or the sound line of the behind-the-ear hearing aid.
Otoplastics and customized ear adaptor members are particularly employed when adapting a hearing aid to the shape of the auditory canal of the ear of the hearing impaired person. Such otoplastics and ear adaptor members, first, function to fix the position of the hearing aid so that the hearing aid cannot slip out or even fall out of the ear. In addition, the otoplastic of the ear adaptor member has a sound dampening effect in order to prevent feedback between the microphone and the ear phone of the hearing aid. Otoplastics are generally formed as an adaptation to the in-the-ear hearing aids (ITE devices), which otoplastics are in contrast to the ear adaptor members which are used for the behind-the-ear hearing aids (BTE devices).
In standard manufacturing methods of otoplastics and customized ear adaptor members, an impression of the auditory canal of the ear of the hearing impaired person to be fitted therewith is first made. A negative then is formed from this first impression. Only then can the otoplastic or the ear adaptor member, which is adapted to the shape of the auditory canal of the ear, be manufactured from this negative. After the manufacture, the otoplastic or ear adaptor member must also be frequently cut or ground in order to eliminate casting errors. Since this process is expensive and time-consuming, many manufacturers have been attempting for some time to develop a method wherein the manufacturing of the formation of the first impression and the negative of the first impression can be eliminated or avoided.
Thus, for example, German AS 12 31 304 discloses a method in accordance wherein a self-curing plastic is distributed on a base member simulating the basic structure of the auditory canal of the human ear and the coated base member is subsequently inserted directly into the auditory canal of the ear of the hearing impaired person and held there until the plastic has now adapted to the inside contour of the auditory canal and has hardened. The adaptation to the inside contour, however, is not yet optimum. There is the risk of pressing plastic too far into the auditory canal due to the impression of the plastic coated basic form into the ear.
In this method, moreover, a multitude of different standard base members are required, since the plastic coating is not adequate in order to sufficiently adapt to all shapes of auditory canals upon employment of a single base member of mandrel. The analogous case applies to the subject matter of the article by Dr. Barry Voroba, "A Tool for the Optimization of Hearing Aid Fittings", Hearing Instruments, Vol. 35, No. 1, 1984, pp 12, 13, 14 and 16. In this case, the soft plastic material is injected into an ear. A suitable die is then pressed into this compound before it hardens.
U.S. Pat. No. 4,006,769, whose disclosure is incorporated by reference and which claims priority from the same Netherlands Application as German AS 24 59 259, discloses another possibility of manufacturing an ear adaptor member without utilizing the impression and a negative. Instead of an otoplastic, the sound canal of a hearing aid is held in the auditory canal with a surrounding liquid-filled pocket or bag. The pocket is adapted to the shape of the auditory canal in that a pressure ring is pressed against the material of the pocket. However, a disadvantage of this particular solution is that the liquid in the pocket does not harden. Thus, there is always the risk that the pocket will tear and the liquid will run out into the ear.
Another method for directly taking the shape of an auditory canal without utilizing the impression and the negative is disclosed in copending U.S. patent application Ser. No. 185,794, filed Apr. 22, 1988, which issued on Oct. 3, 1989 as U.S. Pat. No. 4,871,502 and which was based on German Patent Application P 37 15 082.0. The method disclosed in this application involves injecting a flowing otoplastic material between a die and a sheath drawn over the die and allowing this to harden while the sheath and die are positioned in the ear.
Shaped parts of expanded plastic for ear adaptor members have been developed in recent time. Such shaped parts of expanded plastic have already been known for some time as anti-noise plugs and are manufactured in mass production. An adaptation to the individual auditory canal is not carried out. The expanded plastic parts are merely pressed together and inserted into the ear, whereupon they will again expand and swell. Included among the manufactures of such expanded plastic parts are Grace Chemie, Heidelberg, and 3M, USA. The device manufactured by 3M is disclosed in a sales sheet entitled "COMPLY.sup..TM. Instant Earmold", No. 70-208-2478-0 (77.5) 11, and is also discussed in an article by Sholak et al "Disposable Foam Earmolds", Hearing Instruments, Vol. 38, No. 12, 1987. However, such expanded plastics are less suitable as a pure otoplastic replacement for an in-the-ear hearing aid, since the expanded plastic is too soft. In addition, such expanded plastics are quickly contaminated, such as by cerumen, and must be frequently replaced. Such expanded plastics are not yet optimumly used, even as ear adaptor members.